75 Integrating Membrane Transport with Male Gametophyte ... - TAIR

263 Involvement of Cytokinins and Two-Component Elements in Arabidopsis responses to
pathogens
Cristiana Argueso, Joseph Kieber
University of North Carolina at Chapel Hill
Cytokinins are plant hormones involved in many aspects of plant biology and development, such as regulation of cell
division, senescence and sink-source relationships within the plant. While the plant hormones salicylic acid, jasmonic acid
and ethylene have been implicated in the regulation of plant defense responses against pathogens, the role of cytokinins
remains unclear. Recent studies have revealed that cytokinin signaling involves a phosphorelay pathway similar to twocomponent
element response systems, used by bacteria and other organisms to sense and respond to a diverse array of
environmental stimuli. We have tested Arabidopsis mutants with T-DNA insertions in genes encoding two-component
elements, as well as transgenic lines, for their susceptibility to biotrophic and necrotrophic pathogens. Some of these
mutants show increased or decreased susceptibility to pathogens, indicating a possible role for two-component elements
and cytokinins in Arabidopsis responses to pathogens. It is possible that cytokinins/ two-component elements could play
a role in plant-pathogen interactions either through the activation of plant defense responses or through the regulation
of sink-source relationships within the plant. Our research may help elucidate additional roles of cytokinins in plant
biology, as well as contribute to a better understanding of plant-pathogen interactions and to the generation of plants
with increased disease resistance.
264 Identification of infection-related proteins at the host-pathogen interface of Arabidopsis
Nico Boot 1 , Monique Slijper 2 , Albert Heck 2 , Guido van den Ackerveken 1
1
Molecular Genetics Group, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584
CH Utrecht, The Netherlands, 2 Biomolecular Mass Spectrometry, Department of Chemistry and Department
of Pharmaceutical Sciences, Faculty of Science, Utrecht University, Sorbonnelaan 16, 3584 CA Utrecht, The
Netherlands
The host cell plasma membrane (PM) constitutes an important barrier that restricts extracellular pathogens from
having access to the cytoplasm of the host cell. Being the site of contact between host and pathogen, the PM plays a
key role in nutrient exchange and signal transduction between the interacting organisms. To proliferate extracellularly
pathogens need to suppress host cell defenses and manipulate nutrient metabolism and transport. To achieve this the
bacterial pathogen Pseudomonas syringae pv. tomato (Pst) uses its type III secretion system to inject a plethora of effector
proteins into the host cell cytoplasm. Several of these effectors have been shown to suppress plant defense. However, the
influence of Pst on signaling and transport processes over the PM of the host is unknown. We hypothesize that proteins
involved in these processes are more abundant at the PM during infection. To elucidate the molecular processes occurring
at the host-pathogen interface of Arabidopsis (accession Col-0) with virulent Pst (DC3000 strain) we have isolated PM
of mock-treated and Pst-infected Arabidopsis seedlings. Tryptic digests of the PM fractions were subjected to semiquantitative
LC-MS/MS analysis. We have identified several proteins that show differential presence in Pst-infected vs.
mock-treated PM fractions. Our data indicate that several proteins become PM-associated during the infection process
while their overall protein levels do not increase. Functional studies will elucidate if these PM-associated proteins play
an important role during the infection process.